The invention relates to a device for recirculating exhaust gas during the operation of multi-cylinder internal-combustion engines.
Exhaust gas recirculation is an effective measure for lowering the nitrogen oxide emissions of internal-combustion engines. A device for recirculating exhaust gas is known, for example, from U.S. Pat. No. 5,517,976. There, the cylinders of a supercharged internal-combustion engine are divided into two groups. The waste gas of one group, preferably of a cylinder, is fed by way of an exhaust gas recirculation line, to the intake line of the internal-combustion engine. The waste gas of the other cylinder group is collected in an exhaust gas collection line and is fed to the turbine of an exhaust gas turbocharger. The exhaust gas recirculation line and the exhaust gas collection line are mutually connected by way of a connection line and a valve device which controls a flow cross-section of the connection line.
An analogous device is also illustrated in German Patent Document DE 39 30 243 A1, where a 3/2-way valve is used for switching off exhaust gas recirculation when the internal-combustion engine is cold and the load is low. When the exhaust gas recirculation is switched off, the exhaust gas of the cylinder connected with the exhaust gas recirculation line is directed to the exhaust gas collection line connected to the remaining cylinders. This type of device, which divides the cylinders into two groups, one of which is provided for the exhaust gas recirculation, presents the problem that an arrangement of a valve device is required in the region of the exhaust gas collection line having limited installation space. When the exhaust gas collection line is cooled, the passing of the drive shaft through the water cooling jacket can, in addition, be achieved only at high constructive expenditures.
U.S. Pat. No. 4,249,382 discloses another device that uses a group of exhaust gas cylinders for recirculating exhaust gas. Here, a valve device having two valves is used for controlling the exhaust gas flows. In an embodiment described in the document, a non-return valve is used to prevent combustion air from the air supply line from entering the exhaust gas recirculation line.
German Patent Document DE 19521573 A1 shows a supercharged internal-combustion engine with an exhaust gas recirculation which contains a non-return flap in the exhaust gas recirculation line and a valve for switching off the exhaust gas recirculation. The recirculated exhaust gas is taken from an exhaust gas collection line to which all cylinders of the internal-combustion engine are connected. The disadvantage of this construction is that the exhaust gas composition of the recirculated gas cannot be optimally adjusted because each cylinder cannot be controlled to influence the exhaust gas quality of the recirculated exhaust gas.
The invention addresses the problem of providing a valve device for the exhaust gas recirculation, which requires low constructive expenditures in the region of the exhaust gas collection line. The valve is used for internal-combustion engines having two groups of cylinders, one of which (xe2x80x9cdispenser cylindersxe2x80x9d) provides the exhaust gas for exhaust gas recirculation.
This object is achieved by a valve device described as follows. A nonreturn valve, preferably a flap with a restoring spring divides the exhaust gas collection pipe into two sections. The integration of a non-return valve with a control in the exhaust gas collection line presents no constructive problems even under limited space conditions. The recirculated exhaust gas flows are controlled by a controllable valve in the exhaust gas recirculation line. The arrangement of a controllable valve, together with the drive shaft and the servo motor, in the exhaust gas recirculation line, will cause no problem because of the space available there. In this manner, a solution is achieved which is favorable with respect to the constructive expenditures and the cost.
The invention will be explained in detail by means of an illustrated embodiment.